Field of Invention
The present invention relates to a switching regulator having adjustable inductor current threshold and a control method thereof; particularly, it relates to such switching regulator having adjustable inductor current threshold and such control method capable of adjusting the inductor current threshold of the power stage, so that when the switching regulator operates under a light load mode or even an ultra-light load mode, an optimum balance between total power consumption and switching noise interference is achieved.
Description of Related Art
To supply power to a load, a conventional switching regulator may operate either under a discontinuous conduction mode (DCM) or a continuous conduction mode (CCM).
However, when the conventional switching regulator operates under CCM and under a light load mode, there will be a reverse inductor current (i.e., the sign of the level of the inductor current will be negative), whereby the efficiency of the conventional switching regulator is lowered (as shown by the curve labeled as “prior art 1 (CCM)” in FIG. 4).
On the other hand, when the conventional switching regulator operates under DCM and under a light mode, because the DCM operation has a zero current detection mechanism, when the inductor current flowing through the inductor drops to zero, the lower gate transistor switch will be turned OFF immediately, such that there will be no reverse inductor current (as shown by the curve labeled as “prior art 2 (DCM)” in FIG. 4). Nevertheless, such “prior art 2 (DCM)” still has a drawback, which is: when the conventional switching regulator operates under DCM and under an ultra-light load mode, the switching frequency of the conventional switching regulator will gradually decrease, resulting in undesirable noise interference.
Therefore, either the conventional switching regulator operates under DCM or CCM, there is a dilemma of either occurrence of an undesirable noise interference or low power efficiency under a light load mode. Because the switching regulator in many communication systems nowadays (for example, a smart phone) is often required to operate under a light load mode, it is vital for the switching regulator, especially under a light load mode, to ensure an optimum balance between power switching efficiency and switching noise interference.
In view of the above, to overcome the drawbacks in the prior art, the present invention propose a switching regulator having adjustable inductor current threshold and a control method capable of adjusting the inductor current threshold of the power stage, so that when the switching regulator operates under a light load mode or even an ultra-light load mode, an optimum balance between power switching efficiency and switching noise interference is achieved.